Add-on and Add on

Add-on noun - Something that is not necessary in itself but adds to the convenience or performance of the main piece of equipment.

Add on and add-on are semantically related In some cases you can use "Add on" instead a noun phrase "Add-on".

Add on verb - Make an addition.

Add-on and add on are semantically related in added ingredient topic. You can use "Add-on" instead a noun "Add on".